The present invention relates to a device for measuring the pulling-in force to which a tool support part, such as a tool system module in the form, for example, of a basic tool mounting means, is subjected during coupling to an associated handling device, such as a spindle of a machine tool in the form, for example, of a drilling machine, lathe or milling machine, during operation of a clamping system provided on the handling device. Any component provided with a suitably adapted clamping system for coupling of a tool support part including, for example, a further tool system module, can be regarded as such a handling device.
In the course of industrial development of modern manufacturing installations equipped with automatic tool-changing systems, the need for tool systems of modular construction has become increasingly greater. As an example, there is used in the basic tool mounting means of such systems a clamping shank manufactured with great precision, to which shank a system of different tools can be coupled. The coupling or clamping system for coupling the basic tool mounting means, an example of which is an HSK (hollow-shank taper) mounting means to a machine-tool spindle must meet stringent requirements as to stable and nonpositive connection in the region of the interface between the components to be coupled. If, for example, the actual pulling-in force is smaller than the specified pulling-in force stipulated by the machine manufacturer, the dynamic relationship between machine-tool spindle and basic tool mounting means deteriorates. This leads to a reduction of cutting performance, increased tool wear, possibly even tool break, shorter useful life, poorer attainable surface quality and stress on the machine-tool spindle and guideways. The magnitude and constancy of the pulling-in force is therefore of paramount importance for coupling of a basic tool mounting means to a machine-tool spindle.
Not only conventional steep-taper interfaces but also numerous other manufacturer-specific interfaces are used in industry as interface connections. The main types, however, are the hollow-shank taper interfaces, in which an axial extension of a component such as the aforementioned basic tool mounting means, which extension is constructed as a hollow-shank taper, is pulled into a matching mounting means on a handling device such as the aforementioned machine-tool spindle, during operation of a clamping system such as a three-claw clamping system.
To ensure the function of the clamping system, or in other words the necessary clamping or pulling-in force, all clamping systems must have the technical test capability of measuring the pulling-in force. The devices for measuring pulling-in force that are now commonplace operate electronically and, because of extremely complex techniques involving strain gauges, are relatively expensive and sensitive to shock and dirt under production conditions. In addition, electronic devices for measuring pulling-in force require a supply of energy from, for example, the power line or batteries.
As an example, there is known from German Unexamined Application 3829846 an electronic system for measuring the pulling-in force of tool-clamping jigs of machine tools, which are provided with a spindle tool mounting means for a tool shank and a clamping member for axially clamping the tool shank on the tool mounting means. The system for measuring pulling-in force comprises a test shank formed in one piece on the tool mounting means and designed for clamping connection to the clamping member, which shank is provided with a measuring member influenced by the clamping force for influencing a sensing device for the clamping force. The measuring member is a measuring body which senses the clamping force by mechanical deformation, and which can comprise, for example, one or more strain gauges.
The object of the present invention is now to provide, for measuring the pulling-in force to which a tool support part is subjected during coupling to an associated handling device, a device for measuring pulling-in force which, compared with the conventional devices for measuring pulling-in force, is inexpensive, impact-resistant, insensitive to dirt, of compact construction and operates independently of external energy.
This object is achieved by a device for measuring pulling-in force according to the features of claim 1.
According to the invention there is provided a device for measuring pulling-in force in which the pulling-in force on a pulling-in part is measured on the basis of a certain physical effect, in which a well-defined relationship exists between the force applied to the deformation body via the pulling-in part and the resulting change of shape of the deformation body. Depending on the structural design and the functional interaction of the individual components of the device for measuring pulling-in force, the pulling-in force exerted on the pulling-in part can be transmitted as a tensile or compressive force to the deformation body, whereby the deformation body is subjected to corresponding elongation or compression. From the associated change in length of the deformation body, the force applied to the deformation body and thus to the pulling-in part can ultimately be measured in simple manner, for example by means of a mechanical force transducer, on the basis of the well-defined relationship between force and length change. The inventive device for measuring pulling-in force can therefore operate purely mechanically and completely independently of the power line or batteries. Furthermore, it is characterized by a structure which is relatively simple and therefore inexpensive from the engineering viewpoint, and which can be used successfully in the simplest form without any electronics.
The inventive device for measuring pulling-in force is also characterized by great flexibility of use. Essentially it can be used for measuring the clamping force of all interface clamping systems, or in other words on all common interface connections in which two parts to be coupled are clamped axially to one another. As an example, if the pulling-in force of a basic tool mounting means is to be measured in a mounting means provided on a machine-tool spindle, the inventive device for measuring pulling-in force is coupled instead of the basic tool mounting means to the machine-tool spindle. The inventive device for measuring pulling-in force is therefore provided with constructively essential features that can also be found in a basic tool mounting means, or in other words a support surface which, during coupling to the machine-tool spindle, becomes braced against a support surface provided thereon, as well as a pulling-in part that functions as the pulling-in shank of the basic tool mounting means and that is subjected to the pulling-in force of the clamping system. In contrast to the basic tool mounting means, however, the support surface in the inventive device for measuring pulling-in force is constructively separate from the pulling-in part functioning as the shank, and so the pulling-in part can be moved relative to the support part. The support part and the pulling-in part are connected to one another, as described hereinabove, by the deformation body.
Advantageous embodiments of the inventive device for measuring pulling-in force are subject matter of the dependent claims.
In the improvement according to a second example, the deformation body is also advantageously chosen and, in view of the maximum forces to be expected during operation of the clamping system, is dimensioned such that it is subjected to elastic deformations during operation of the clamping system. In this case a linear force-deformation relationship can be used for measurement of the pulling-in force.
The choice of support-surface pair between the support part and the handling device as annular plane surfaces according to a third example permits stable coupling, free of transverse forces, of the inventive device for measuring pulling-in forces to the handling device, and thus also reliable measurement of the pulling-in force.
The improvement according to a fourth example allows for the fact that conventional tool support parts for coupling to a handling device are often provided with a taper shank to be pulled into an axial mounting means provided on the handling device, and thus it permits the most practical possible measurement of the pulling-in forces applied to the tool support parts.
With the improvement according to a fifth example, the frictional forces that normally occur between the generating surface of the shank portion and the inside generating surface of the mounting means when the shank portion is pulled into the mounting means are excluded, thus permitting measurement of the maximum pulling-in force of the clamping system. The cross sections of the support part, pulling-in part and deformation body are chosen such that the shank portion of the pulling-in part can still be pulled with clearance into the mounting means of the handling device even in the case of development of the maximum forces to be expected and thus maximum length changes.
According to a sixth example, the shank portion preferably has the form of a hollow-shank taper; nevertheless, in view of the shanks that are now commonplace, it can also have a different form, such as the form of a steep taper.
To provide the inventive device for measuring pulling-in force with a structure that is as compact and insensitive to dirt as possible, the support part according to a seventh example advantageously has the form of a bell, which shields from the outside environment a cylindrical portion of the pulling-in part axially adjoining the shank portion as well as the deformation body inserted between the support part and the pulling-in part.
According to an advantageous improvement according to eighth and ninth examples, the deformation body is an extensible body connected firmly to the cylindrical portion of the pulling-in part and/or to the support part, for example by being screwed together therewith, so that in this case a length change proportional to the tensile load is used in the form of elongation of the extensible body for measurement of the pulling-in force. As the extensible body there is preferably used a reduced-shaft bolt. It would also be conceivable, however, to use a spring body.
In connection with the use of a conventional mechanical dial gauge as the device for sensing the deformation of the reduced-shaft bolt, a tenth example shows an advantageous improvement of the reduced-shaft bolt wherein the reduced-shaft bolt is provided with an axial bore, in which there is inserted a pin which is connected functionally to the device for sensing the deformation of the reduced-shaft bolt, the pin being in the case of the dial gauge, for example, an extension of the measuring pin.
With the improvement according to an eleventh example, according to which an adjusting device for adjusting the axial length of the pin is provided, there is obtained in simple manner the capability of precision adjustment of the measurement range of the device for sensing the deformation. According to a twelfth example, the adjusting device is constructed for simplicity as a setscrew, for example a hexagon socket screw, which is screwed into a threaded bore formed in the end portion of the reduced-shaft bolt, which portion is screwed together with the cylindrical portion of the pulling-in part.
The improvement according a thirteenth example, according to which the shank portion is cylindrical, provides a further possible application of the inventive device for measuring pulling-in force; for example, the principle of the inventive device for measuring pulling-in force can also be applied to a VDI shank interface connection.